Theta series of direct sum of 3 copies of hexagonal lattice.

Terms

a(0) =1a(1) =18a(2) =108a(3) =234a(4) =234a(5) =864a(6) =756a(7) =900a(8) =1836a(9) =2178a(10) =1296a(11) =4320a(12) =3042a(13) =3060a(14) =5400a(15) =6048a(16) =3690a(17) =10368a(18) =6588a(19) =6516a(20) =11232a(21) =11700a(22) =6480a(23) =19008a(24) =12852a(25) =10818a(26) =18360a(27) =19674a(28) =11700a(29) =30240